The present invention relates to a confocal imaging system for in vivo clinical examinations of dermal and subdermal tissues, and particularly to a confocal imaging system of a patient""s skin tissue which minimizes instability in confocal images by reducing the relative motion of the tissue with respect to the confocal imaging optics of the system. This invention is especially suitable for providing an instrument or attachment for dermal pathological applications.
Systems have been proposed for confocal scanning of skin, such as described in Rajadhyaksha et al., xe2x80x9cIn vivo Confocal Scanning Laser Microscopy of Human Skin: Melanin provides strong contrast,xe2x80x9d The Journal of Investigative Dermatology, Volume 104, No. 6, June 1995, pages 1-7. These systems have confocal optics which direct light to the patient""s skin tissue and image the returned reflected light. Such optics have a limited field of view of the patient""s skin tissue, which for example may cover a tissue area less than one millimeter wide. One problem with these systems is that motion of the patient during confocal imaging can cause the tissue area being imaged to move relative to the system""s confocal optics, shifting the field of view of the tissue area with respect to the optics. Consequently, confocal images from such systems may appear unstable to the viewing physician, making it difficult for the physician to observe dermal structures of interest. Even slight motion of the patient""s skin tissue, such as due to involuntary muscle movement in adjacent tissue or from a circulatory pulse, can cause dermal structures of a confocal image to appear to move in and out of the imaged tissue area.
Accordingly, it is the principal object of the present invention to provide an improved system for confocal imaging within dermal and subdermal tissue of a patient which minimizes instability in confocal images by reducing the relative motion of the tissue with respect to the confocal imaging optics of the system.
It is another object of the present invention to provide an improved system for confocal imaging of tissue having a mechanical structure, such as a platen, brace, or attachment which both supports the confocal imaging optics of the system and applies stress to a limited surface area of the tissue to minimize skin motion during confocal imaging.
Briefly described, the system embodying the present invention includes a mechanism for maintaining an area of skin tissue under stress by application of force at the edges of the area, and an imaging head coupled to this mechanism for imaging the stressed skin. The mechanism and imaging head provide an integrated assembly. In one embodiment, the mechanism of the system for maintaining an area of skin tissue under stress is provided by a platen, which is positionable with respect to the patient having the skin tissue to be examined. The imaging head is coupled to the platen and is positioned for imaging through an orifice in the platen. To position the platen with respect to the patient, the patient is supported by a table and the platen rides in a carriage upon rails over the patient. The carriage and platen assembly may be temporarily locked in position upon the rails. Another mechanism is provided in the system for moving the platen from an up position in the carriage, where the platen is spaced from the patient, to a down position onto the surface of the skin tissue of the patient, such that in the down position the force of the platen stresses the skin tissue within the orifice of the platen.
In a second embodiment, the mechanism of the system for maintaining an area of skin tissue under stress is provided by a brace supporting the imaging head. The brace has an opening through which the imaging head images the skin tissue. The brace is restrained by straps to the body part of the patient having the skin tissue in order to force the brace against the skin tissue, thereby stressing the skin tissue within the opening of the brace. The brace may further include an upper lamination, coupled to the imaging head, and a lower lamination, coupled to the restraining straps, which provides the opening of the brace. The lower lamination has slots for receiving the upper lamination in which the upper lamination is movable within the slots over the lower lamination and temporarily fixable within respect to the lower lamination. The upper lamination has an aperture (or window) substantially smaller than the opening in the lower lamination. Through the aperture of the upper lamination, the imaging head images the stressed skin tissue within the opening of the lower lamination.
In a third embodiment, the mechanism of the system for maintaining an area of skin tissue under stress is provided by an attachment having an inner window member and a flexible diaphragm member extending radially from the inner member. A suction mechanism is provided for creating a vacuum between the attachment and the surface of the skin tissue to force the skin tissue against the inner member, thereby stressing the skin tissue adjacent to the inner member. The imaging head images the stressed skin tissue through the window member. The diaphragm member may further include a semi-rigid ring along its outer periphery and an annular protruding section which defines inner and outer cavities when the attachment is adjacent to the skin tissue. The suction mechanism may then selectively create suction in the inner and outer cavities, when the attachment is adjacent to the skin tissue, to pull the skin tissue into the cavities and stress the skin tissue adjacent to the inner member.
The three embodiments of the system are particularly suitable for imaging external tissue in different regions of the patient""s body. The platen may be used for confocal imaging of skin tissue on the chest or back. The brace may be used for gross anatomical features, such as the arm, leg or torso, around which the straps can hold the brace upon. The attachment is useful for smaller regions of the skin, where there is no gross anatomical feature, or where the surface of the skin tissue in not substantially level.